Skip to main content

Full text of "The Cambridge Natural History"

See other formats


MuuateeI differs  from the blubber of the Whale io  that  there
is no free oil anywhere.2
The skeleton of the Sirenia is strong and massive, thus con-
trasting with the loosely-textured bones of the Cetacea. The
cervical vertebrae arc, as a rule, free, but the second and third are
fused in Matmtvs and the extinct Ifalitherium. It Is noteworthy
that iu Ithytina the cervical vertebrae have the exceedingly thin
centra that characterises the neck vertebrae in Whales. The ribs
are most of them, firmly articulated by two heads. The breast-
bone is generally reduced, as iu Whales; and bat few ribs are
attached thereto. The vertebrae, moreover, are well locked to-
gether by zyj^apophyses, and not loosely attached as in "Whales,
The shoulder blade is long and narrow, and not unlike that of
the Seals. It is totally unlike the peculiarly-modified scapula
of the Whale trite. But, as in the latter, there are no clavicles.
The hind-limbs are only represented by the pelvis; and this
is a ru'.liini'ntury structure, varying, however, in the degree of its
degeneration. That of the extinct JETalitherium recalls the pelvis
of the Ilor«|iixii. There is a single triradiate boue with an aeeta-
bulur cavity for the rudiment of the femur in the centre; it
suggests that here the three normal elements of the pelvis have
become fused into a single "bone* In the Uogong there are two
small bones GO. each side.
The Manatees (ATanatu-s) 3 are found in the fresh-waters and
along the Atlantic coasts of South America and Africa, It
appears that there are four species, of which one only is African,
the others American. Report asserts the former occurrence of
this genus on the shores of St. Helena.
The Manatee is provided with only six cervical vertebrae, a
fact which distinguishes it from the other existing genera of its
group. A remarkable feature which it exhibits is the large
number of molar teeth. These apparently go on increasing in-
definitely during its life, the suggestion, being that they are worn
away by the nature of the food—algae with much sand intermixed.
As many as twenty molar teeth have been counted in one half of
the jaws and there is no reason to forbid the assumption that they
1 Kiikeiithal lias dlscoTered a thick coating of radiroentary hairs in the fbettw
of the Maaatee, tlras sIxawiBg that it is the daaoendaiit of an animal ferry Ilk®
a Seal.
*  " On the MftB&tee," i** Trans, JSbdL Sac. roL yiiL 1872, p» tSff.
*  Etartlttib, * * BeitrSg® zur Keuatnis te Man»to»-Jxton»" %&&L JfefeA, 188% p. 1*